This invention relates to a water treatment system and particularly to one utilizing a reverse osmosis unit from which both the low mineral product water and the waste water are used by the associated water using equipment.
Commercial ice makers are susceptible to breakdown due to the accumulation of lime scale and other precipitates which may form from the minerals found in the water used to make the ice. The water used to make the ice usually is allowed to flow into a reservoir, from which it is recirculated over a freezing plate and back to the reservoir. This process encourages the rinsing away of dissolved minerals and other impurities from the growing mass of crystalline ice and back into the reservoir where the concentration of minerals increases. Some of this concentrated water is conserved for the next successive ice making cycle, resulting in a continual compounding of the concentrating effect of the process from cycle to cycle. Usually a good portion of the concentrate is flushed or dumped from the ice machine after each cycle to help slow the compounding of the concentrating effect in an attempt to extend the time between ice machine cleanings. This leads to inefficiency, since the water dumped has already been chilled to near freezing temperature, and the new make-up water let in to replace the dumped water has not been chilled. Eliminating or reducing the amount of the dump would make the ice machine operate more efficiently.
Commercial steam cookers are also similarly susceptible to such scale formation and equipment breakdown. Water entering the boiler is turned to steam, which enters the cooking chamber, leaving the minerals from the water behind to concentrate in the boiler. Heating of the water to above its boiling point leaves behind the dissolved minerals to precipitate as scale or sludge leading to machine breakdown and/or increased maintenance.
Many ice makers are water-cooled. The water used for this purpose removes heat from the refrigerant and allows the refrigerant to condense from a gas back to a liquid for repeated use in the machine. The water used as cooling water is usually tap water and goes down the drain after passing through the condenser of the ice machine.
Steam cookers also use water for cooling. The cooking chamber has an outlet to allow the condensed steam to drain out of the chamber. The drain pipe also includes a spray condenser, which condenses any steam escaping the chamber. Plumbing codes forbid sending steam or very hot water into the sewer pipes, so cold water is sprayed into the drain pipe to condense the steam and to lower the temperature of the water to be drained. The water used as condensing water is usually tap water.
The use of water low in mineral content in both ice makers and to generate steam in steam cookers would greatly reduce scale formation and extend the time between maintenance calls resulting from scale build-up. Also the ice machine dump could be reduced or eliminated with the use of water of low mineral content.
Osmosis is the passage of liquid through a semi-permeable membrane. A semi-permeable membrane is a membrane which allows one component of a solution to pass through it and not the others. In osmosis, there is a tendency for liquid to go from an area of less concentration to an area of more concentration through a semi-permeable membrane. If a pressure is applied to the concentrated solution, reverse osmosis will take place. The pressure causes a flow through the membrane into the diluted solution. When this process is applied to water, the product water that has gone through the membrane has a reduced mineral, or total dissolved solids (T.D.S.), content as a result of the passage of water molecules through the membrane while the mineral ions are rejected and stay behind. The minerals left behind are concurrently washed out by a flow of water termed as waste water or reject water, so that the process of reverse osmosis can continue without the membrane surfaces being scaled over by the mineral build up. This waste water is a major portion of the water that enters the reverse osmosis unit and is directed to the drain.
Because of the desirablility of using water of as low a mineral content as possible in various types of water using equipment such as ice makers and steam cookers it has become desirable to develop a water supply system using the reverse osmosis process and a reverse osmosis unit as a part thereof. In such a system it then also becomes possible to use the waste water generated from the reverse osmosis process as cooling or condensing water for the same units of equipment to which the low mineral water is supplied. Thus, multiple uses of the water supply can be achieved.